This invention relates generally to traffic control systems. More specifically, the present invention relates to a traffic information gathering system using cellular phone networks for automated intelligent traffic signal control.
Intelligent traffic control systems comprise three major components: hardware, traffic control models, and information gathering systems.
After briefly reviewing the first two components, we will present the state of the art of conventional information gathering systems.
Numerous Traffic Signal Controllers are used extensively throughout the United States and elsewhere around the globe. Most controllers are computer activated and use sophisticated software models to achieve optimization of traffic flow.
In the context of the present invention, we will concentrate on the operating models and algorithms that control such traffic signal controllers. Traffic control models underwent a radical change in the mid-1960""s when digital computers began to be increasingly utilized in traffic control systems. Computers allowed creation of actuated controllers that have the ability to adjust the signal phase lengths in real time in response to traffic flow.
Modes of controller operation can be divided into three primary categories: Pre-timed, actuated (including both semi-actuated and fully actuated), and traffic responsive. Under pre-timed operation, the master controller sets signal phases and cycle lengths at predetermined rates based on historical data. Actuated controllers operate based on traffic demands as registered by the actuation of vehicle and/or pedestrian detectors.
Semi-actuated controllers maintain green on the major street except when vehicles are detected on minor streets, and always return right of way to the major street. Fully actuated controllers rely on detectors for measuring traffic flow on all approaches and make assignments of the right of way in accordance with traffic demands.
Traffic responsive controllers respond to inputs from traffic detectors and may react in one of the following ways:
Use vehicle volume data as measured by traffic detectors;
Perform pattern matching: the volume and occupancy data from system detectors are compared with profiles in memory, and the most closely matching profile is used for decision-making;
Perform future traffic prediction: projections of future conditions are computed based on data from traffic detectors.
As the use of traffic responsive controllers has been gaining momentum, the importance of methods of gathering information has also greatly increased.
Conventional Methods of Gathering Traffic Condition Information
Due to ever increasing traffic volumes, traffic control and information acquisition have become a central part of the overall traffic management strategy. Numerous computerized traffic models have become dependent on real time traffic event updates in complex traffic signaling applications.
Generally, dynamic traffic data are gathered by three methods:
1. Road sensor devices such as induction loops, traffic detectors, and TV cameras mounted on poles;
2. Mobile traffic units such as police, road service, helicopters, weather reports, etc.
3. Cellular mobile communication systems, using GPS or similar equipped vehicle-tracking services, usually in closed environments, such as individual private organizations, or commercial entities.
The disadvantages of these conventional data collection methods can be summarized as follows:
1. Relatively high cost of capital investment to install fixed road devices, especially in existing road infrastructures;
2. Relatively limited number of organizations such as trucking, delivery and other service companies utilizing GPS reporting vehicles and relying on proprietary rights of the collected traffic data;
3. Apart from the relatively small number of cars equipped with required GPS devices necessary for precise position determination, generally only small geographical areas are effectively covered due to specific nature of service tasks.
One conventional way to measure traffic flow is by using buried loops in the pavement. These loops create a magnetic field, which is disturbed by the magnetic materials in a car passing over it. A special device in the traffic control cabinet monitors the buried loop and reports to the controller when it has been disturbed. Sometimes microwave detectors resembling a closed circuit TV camera mounted on a pole are used.
Some work has been done recently on mobile traffic data generation using GPS reporting devices mounted on individual cars to provide positioning information of the vehicle via a wireless mobile communication system.
These conventional systems can also provide information on road conditions, weather conditions, etc. The expenditures related to these mobile systems are much more cost-effective than the traditional methods using fixed road metering (such as that disclosed in U.S. Pat. No. 6,012,012 to Fleck et al.). The disadvantage of these systems is the relatively limited number of cars equipped with required GPS devices necessary for precise position determination. Therefore, only a relatively small geographical areas that can be effectively covered.
In another conventional system, GSM phones are combined with built-in GPS devices to enable hybrid location capabilities, based on the GSM network as well as an integral GPS receiver. Mobile Phone Telematics Protocol (MPTP) facilitates hybrid positioning, transferring and managing of information. Mobil phone providers integrate resource management, traffic reporting, telematics, safety and security systems and provide the data to their mobile terminals. With the help of MPTP, cell phones are connected to an existing emergency center and can obtain position updates and emergency call messages. GSM/GPS phones can also provide a wide range of optional features, such as safe area tracking, route navigation, and position requests.
The present invention proposes a system and method that overcomes the shortcomings of conventional traffic data gathering systems by utilizing the general wireless (cellular) telephone information network data. The exemplary system and method is equally compatible with the GSM, CDMA or PDC wireless telephone systems, since it does not depend on system specific features. The data from moving vehicles is collected and fed into the system continuously. The system filters and cleans the data by applying intelligent heuristic algorithms and produces information on traffic situations in real time that can be supplied to automated traffic controllers. This eliminates the need for developing a dedicated mobile wireless information gathering fleet or other high cost devices requiring a large amount of personnel and long reaction times for traffic events such as accidents and traffic congestion.
In brief, the advantages of the exemplary information collection system of the present invention over the prior art sensor based systems may be summarized as follows:
Advantages
1. No need for costly infrastructure: detectors, loops, etc.;
2. Low recurring costs associated with obtaining information;
3. Comprehensive coverage of large geographical regions;
4. Constant improvement in measurement precision;
5. Information stored in the database allows for the performance of various tasks which are difficult or impossible to perform under traditional methods of data collection, such as studying travel profiles, calculating travel times under congestion conditions, calculating various statistics related to roads, road sections, etc.
In view of the shortcomings of the prior art, it is an object of the present invention to provide a system and method for optimizing traffic flow based on information received from wireless telephone systems.
The disadvantages of the prior art may be overcome by using the wireless networks as the means to provide location information as described herein. Technologically, this may be achieved by measuring the signals traveling between a moving cell phone and a fixed set of base stations. This approach takes advantage of the large pool of existing cell handsets. For example, in the United States along there are presently about 50 million cellular handsets. And any necessary modifications, such as specialized location equipment, can be placed on the network rather than in the handsets.
The present invention comprises an intelligent data gathering and processing system based on existing cellular phone networks, and utilizes real time cell phone position data for reconstructing concurrent traffic conditions.
A primary function of the exemplary system of the present invention is the construction and maintenance of lists of vehicles moving along all road sections at particular points in time. This may be achieved by tracking all in-vehicle cell phones within a given region. At each moment, the system maintains a series of such lists associated with a limited number of past consecutive moments. This allows the system to obtain accurate estimates of the total number of vehicles traveling on each specific road section, together with their direction of travel and average velocity. Based on these data, the system is able to 1) compute real time traffic loads for various roads and road sections, 2) generate detailed lists of vehicle turning movements, real time turning data for all relevant intersections, and 3) other traffic parameters. The resulting information can then be passed on with minimum delay to the automated traffic control systems for the purpose of adjusting signal intersection timings to calculate other traffic related parameters of interest.
To achieve these purposes, the system uses the position data of a plurality of cell phones, whether located in moving vehicles, held by pedestrians in moving, or stationary positions, and processes them in an intelligent way to translate their coordinates into relevant traffic information. The system utilizes heuristic algorithms to differentiate between vehicle based cell phones and other cell phone users. Furthermore, the system identifies multiple phone users in a common vehicle to combine them into a single vehicular entity.
Once each group of cell phones has been associated with a common vehicle, it""s the vehicle""s position is calculated, recorded in the database, and assigned to an appropriate road section according to the coordinates of its cell phones at a particular moment.
After recording a pre-assigned number of these positions in a particular time interval, the system generates a continuos path profile (or movement profile) for a given vehicle. Such path profiles constructed and stored as for a large number of vehicles make it possible to calculate traffic loads for all road sections, turning movement volumes at various intersections, and other parameters that can be fed as inputs into traffic control systems. Moreover, the dynamic plurality of path profiles enables the preparation of statistical traffic data tables, the calculation of statistical predictions of travel times along road sections, and the obtaining of other desirable traffic condition parameters.
Obviously, the success of these tasks depends on the quality of initial location data. Improvements in the location technology of wireless networks will undoubtedly lead to new improved performance of traffic information gathering systems and their applications to Intelligent Transportation Systems.
The exemplary system and method is expected to and enhance the overall traffic control capabilities of conventional systems by providing a maximum range of traffic related information.